In this task, we ask you to rewrite a sentence in simple English without changing its general meaning. Essentially, you want to make the sentence easier to read by using simpler words, utilizing more straightforward sentence structures, and omitting non-essential information etc.

A federation ( also known as a federal state ) is a political entity characterized by a union of partially self-governing provinces , states , or other regions under a central federal government ( federalism ) .
A federation is a union of a number of self-governing states or regions , which are joined together under a central government .